Evaporating heat transfer characteristics of R744 - The effect of evaporating temperature and the efficacy of small amount R600a blending to R744

In view of the ozone depletion and the global warming, it is an urgent need to convert from HFCs to natural refrigerants. Among the several candidates of natural refrigerants, 8744 which has an excellent thermal property is suitable for the practical application. Additionally, R600a is already applied as a household refrigerator and its GWP and ODP are almost zero. Under these circumstances, the purpose of this research is to grasp the feature of the evaporating heat transfer and the hydraulic characteristics of pure 8744 and the binary 8744 and R600a mixture. The main test section is a stainless steel tube with the ID of 3.0 mm, which is directly heated by electricity from an electric pole. Evaporating temperature(-30 similar to 10 degrees C) in pure 8744 and R600a mixing fraction (0 similar to 5 wt%) is adopted as the experimental parameters. Finally, to propose the widely available correlation for the thermal and hydraulic characteristics of pure 8744 in tube evaporation phenomena, we derive the empirical correlation in consideration of the evaporating temperature and the tube diameter in this paper.